Connection-structure of a flexible tube

ABSTRACT

A connection-structure of a flexible tube, in which the flexible tube is fitted to an end portion of a metal pipe, comprises an annular projection, a first radially enlarged portion, a seal ring and a second radially enlarged portion. The annular projection is formed on an outer surface of the end portion of the metal pipe. The first radially enlarged portion is formed on the tip side of the metal pipe relative to the projection, defining a first annular groove with the projection. The seal ring is fitted into the annular groove. The second enlarged portion is formed on the base side of the metal pipe relative to the projection, defining a second annular groove with the projection. The tip portion of the flexible tube is positioned close to the maximum diameter portion of the second enlarged portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a structure for connecting a flexibleor resin tube to an end portion of a metal pipe.

2. Description of the Related Art

Conventionally, there is known a connection-structure as disclosed inJapanese Unexamined Patent Publication No. 2006-090416. In thisconnection-structure, an end portion of the metal pipe is provided withat least two radially enlarged portions, and a seal ring is positionedin an annular groove formed between the radially enlarged portions. Aflexible tube is fitted to the metal pipe such that the tip portion ofthe flexible tube passes over the two radially enlarged portions.

In the conventional structure, however, the tip portion of the flexibletube tends to expand because of an operation in which the flexible tubeis connected to the metal pipe, so that a gap is formed between theflexible tube and the metal pipe, increasing the possibility for wateror dust to accumulate in the gap. Due to this, the metal pipe rustseasily, and therefore, it is necessary to use material for the metalpipe that is resistant to rust, such as stainless steel, or to carry outan operation in which an outer surface of the metal pipe is painted, andso on.

SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to improve thetightness of the fitting between the flexible tube and the metal pipe,so that it becomes hard for water or dust to enter between the flexibletube and the metal pipe.

According to the present invention, there is provided aconnection-structure of a flexible tube, in which the flexible tube istightly fitted to an outer surface of an end portion of a metal pipe.The connection-structure of the flexible tube comprises an annularprojection, a first radially enlarged portion, a seal ring, and a secondradially enlarged portion. The annular projection is formed on the outersurface of the end portion of the metal pipe, and circumferentiallyextends over the whole circumference of the metal pipe. The firstradially enlarged portion is formed on the tip side of the metal piperelative to the annular projection, and defines a first annular groovewith the annular projection. The seal ring is fitted into the firstannular groove. The second radially enlarged portion is formed on thebase side of the metal pipe relative to the annular projection, anddefines a second annular groove with the annular projection. The tipportion of the flexible tube is positioned close to the maximum diameterportion of the second radially enlarged portion.

BRIEF DESCRIPTION OF THE DRAWINGS

The object and advantages of the present invention will be betterunderstood from the following description, with reference to theaccompanying drawings in which:

FIG. 1 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a first embodiment of thepresent invention;

FIG. 2 is a cutaway side view showing an upper-half section of the metalpipe of the first embodiment;

FIG. 3 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a second embodiment;

FIG. 4 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a third embodiment;

FIG. 5 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a fourth embodiment;

FIG. 6 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a fifth embodiment;

FIG. 7 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a sixth embodiment; and

FIG. 8 is a cutaway side view showing an upper-half section of aconnection-structure of a flexible tube of a seventh embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is described below with reference to theembodiments shown in the drawings. Each embodiment is aconnection-structure of a flexible tube and a metal pipe, utilized in afuel filler pipe for an automobile, through which fuel is channeled froma fuel filler opening to a fuel tank.

FIG. 1 shows a first embodiment, in which a metal pipe 10 horizontallyextends from the left side such that an opening 11 faces the right side.A flexible or resin tube 30 horizontally extends from the right side,and is tightly fitted to an outer surface of an end portion of the metalpipe 10.

An annular projection 12 is formed on the outer surface of the endportion of the metal pipe 10. The annular projection 12circumferentially extends over the whole circumference of the metal pipe10. In the embodiment, the annular projection 12 is formed using a spoolprocessing technique. A first radially enlarged portion 14 is formed ona portion closer to the tip 13 of the metal pipe 10 relative to theannular projection 12. The first radially enlarged portion 14 extendsparallel to the annular projection 12 to define a first annular groove15 with the annular projection 12. The first annular groove 15 has theshape of an outward-facing open channel, in which a seal ring 16 isfitted. The seal ring 16 is an O-ring, and is made of fluorocarbonpolymers, for example.

A second radially enlarged portion 17 is formed on the base side (i.e.,a portion opposite to the tip 13) of the metal pipe 10 relative to theannular projection 12. The second radially enlarged portion 17 extendsparallel to the annular projection 12 to define a second annular groove18 with the annular projection 12. The second annular groove 18 has agreater breadth than that of the first annular groove 15, and a sealring is not provided.

The first radially enlarged portion 14 is formed using a bulgingtechnique, and the second radially enlarged portion 17 is formed using aspool processing technique. The second radially enlarged portion 17 isbulged in comparison with portions adjacent thereto.

The diameter of the outer surface of the metal pipe 10 on the oppositeside of the second annular groove 18 with respect to the second radiallyenlarged portion 23 is substantially the same as that of the secondannular groove 18.

As shown in FIG. 2, an outer surface of the first radially enlargedportion 14 is a first tapered surface 21 of which the diameter becomessmaller as the distance to the tip portion of the metal pipe 10decreases. An outer surface on the side of the second radially enlargedportion 17 nearest to the second annular groove 18 is a second taperedsurface 22 of which the diameter becomes smaller as the distance to thesecond annular groove 18 decreases. An outer surface of the secondradially enlarged portion 17 that is on the opposite side to the secondtapered surface 22 is a third tapered surface 23 that is inclined in theopposite direction of the second tapered surface 22. The inclinationangles of the second and third tapered surfaces 22, 23 are substantiallythe same, and are steeper than the first tapered surface 21.

The maximum diameters of the annular projection 12, and the first andsecond radially enlarged portions 14, 17 are substantially identical,and are slightly less than the outer diameter of the seal ring 16 fittedinto the first annular groove 15.

The flexible tube 30 is made of polyamide resin, fluoroplastics, olefinresin, and so on, and the inside diameter of the flexible tube 30 isslightly less than the outside diameter of the metal pipe 10. Therefore,in a state in which the flexible tube 30 is press-fitted to the metalpipe 10, the flexible tube 30 is in tight contact with the metal pipe 10in a liquid-proof manner. That is, an inner surface of the flexible tube30 is hermetic or in tight contact with the first tapered surface 21 ofthe first radially enlarged portion 14, the seal ring 16, the secondannular groove 18, the second tapered surface 22 of the second radiallyenlarged portion 17, and a part of the third tapered surface 23. The tipportion 31 of the flexible tube 30 is positioned close to the maximumdiameter portion of the second radially enlarged portion 17, and reachesan edge of the third tapered portion 23, passing over the second taperedsurface 22. The amount by which the tip portion 31 of the flexible tube30 protrudes from the peak of the second radially enlarged portion 17,i.e., the boundary between the second tapered surface 22 and the thirdtapered surface 23, to the third tapered surface 23, is 0.5-5.0 mm.

An outer surface of the metal pipe 10 is painted for rust-prevention,but because the flexible tube 30 is tightly fitted to the end portion ofthe metal pipe 10, the painted portion of the metal pipe 10 can bereduced. More concretely, on the outer surface of the metal pipe 10 aportion (A) up to the second annular groove 18, to which the tip portionof the flexible tube 30 is fitted tightly, should be painted. A portion(B) of the second annular groove 18, where the flexible tube 30 isseparated from a surface of the groove 18, i.e., a part close to theannular projection 12 and a wall of the side of the second annulargroove 18, may be painted depending upon the condition. Conversely, fromthe annular projection 12 to the tip portion 13 of the metal pipe 10need not be painted.

In a connecting operation of the metal pipe 10 and the flexible tube 30,the tip portion 13 of the metal pipe 10 is placed in line with the mouthof the flexible tube 30, and the metal pipe 10 is gradually insertedinto the flexible tube 30. Due to this, the end portion of the flexibletube 30 is expanded by the first tapered surface 21, and passes over theseal ring 16 and the annular projection 12, to reach the second annulargroove 18. The metal pipe 10 is then further inserted into the flexibletube 30, and this connecting operation is completed when the tip portion31 reaches the position slightly over the peak 24 of the second taperedsurface 22, i.e., by 0.5-5.0 mm.

In this connecting operation, the metal pipe 10 may be inserted into theflexible tube 30 while an outer surface 19, which is the base side ofthe metal pipe 10 relative to the second radially enlarged portion 17,is fixed by a jig and so on. Thus, since the jig is engaged with thesecond radially enlarged portion 17, the metal pipe 10 can be stronglypressed, so that the connecting operation is easy.

In a state in which the flexible tube 30 is connected to the metal pipe10, the tip portion 31 of the flexible tube 30 is positioned slightlyover the peak 24 of the second tapered surface 17, and positioned on anedge of the third tapered surface 23. Therefore, the tip portion 31 ofthe flexible tube 30 is expanded by the second radially enlarged portion17, so that a tension force greater than that in the other portions isgenerated in the tip portion 31. That is, the tip portion 31 is in tightcontact with the second radially enlarged portion 17 in a liquid-proofmanner, so that water, dust, and so on is prevented from enteringbetween the metal pipe 10 and the flexible tube 30, decreasing thepossibility of material causing rust to accumulate. Therefore, the metalpipe 10 hardly rusts, and a surface area in the end portion of the metalpipe 10, which should be painted for rust-prevention, can be reduced.

FIG. 3 shows a second embodiment.

The difference from the first embodiment is a shape of the secondradially enlarged portion 41. The inclination angle of the secondtapered surface 42 of the second radially enlarged portion 41 and theinclination angle of the first tapered surface 21 are substantially thesame. Further, the second radially enlarged portion 41 has a verticalsurface 43, positioned on the opposite side of the second taperedsurface 42, and the vertical surface 43 is substantially perpendicularto the outer surface of the metal pipe 10. The tip portion 31 of theflexible tube 30 passes over the second tapered surface 42, and reachesthe upper edge of the vertical surface 43. The other structures areidentical to the first embodiment.

According to the second embodiment, similar effects as the firstembodiment can be obtained. In addition to these effects, due to thevertical surface 43 of the second radially enlarged portion 41, a jigbecomes easily engaged with the second radially enlarged portion 41 ofthe metal pipe 10 in a connecting operation of the metal pipe 10 and theflexible tube 30, and thus a pressing operation of the metal pipe 10becomes easier than the first embodiment.

FIG. 4 shows a third embodiment.

The differences from the first and second embodiments are a secondradially enlarged portion 44 and an outer surface of the metal pipe 10.A second tapered surface 45 of the second radially enlarged portion 44has the same inclination angle as the first tapered surface 21,similarly to the second embodiment. Conversely, an outer surface 46 ofthe second radially enlarged portion 44, opposite to the second taperedsurface 45, is a cylindrical surface having substantially the samediameter as the maximum diameter of the second radially enlarged portion44. The tip portion 31 of the flexible tube 30 passes over the secondtapered surface 45, and reaches an edge of the outer surface 46. Theother structures are identical to the first and second embodiments.

In the third embodiment, since the diameter of the base portion of themetal pipe 10 with respect to the second radially enlarged portion 44 isthe same as the maximum diameter of the second radially enlarged portion44, the diameter of the tip portion 31 of the flexible tube 30 cannot bereduced in a state in which the tip portion 31 of the flexible tube 30is positioned over the second radially enlarged portion 44. Therefore, agap cannot open up between the tip portion 31 of the flexible tube 30and the metal pipe 10.

FIG. 5 shows a fourth embodiment.

The fourth embodiment has a similar structure as the first embodiment.The point different from the first embodiment is that the seal ring 16and a back-ring 47 are fitted into the first annular groove 15. Theback-ring 47 is in contact with the annular projection 12, and the sealring 16 is in contact with a side surface of the first radially enlargedportion 14. The other structures are identical to the first embodiment,and the effect and operation are identical to the first embodiment.

FIG. 6 shows a fifth embodiment.

The fifth embodiment has a structure that resembles the secondembodiment. The point different from the second embodiment is that theseal ring 16 and the back-ring 47 are fitted into the first annulargroove 15. The other structures are identical to the second embodiment,and the effect and operation are identical to the second embodiment.

FIG. 7 shows a sixth embodiment.

The sixth embodiment has a structure that resembles the thirdembodiment. The point different from the third embodiment is that theseal ring 16 and the back-ring 47 are fitted into the first annulargroove 15. The other structures are identical to the third embodiment,and the effect and operation are identical to the third embodiment.

FIG. 8 shows a seventh embodiment.

The basic structure of the seventh embodiment is the same as that of thefirst embodiment, but the position of the tip portion 31 of the flexibletube 30 is different. That is, although the position of the tip portion31 of the flexible tube 30 is close to the maximum diameter portion ofthe second tapered surface 22, the tip portion 31 does not reach thepeak 24 of the second radially enlarged portion 17, but is positioned onthe second tapered surface 22. The tightness of fit between the flexibletube 30 and the metal pipe 10 is inferior to the first embodiment, butsuperior to a conventional structure. Thus, water or dust are preventedfrom entering between the flexible tube 30 and the metal pipe 10.

The present disclosure relates to subject matter contained in JapanesePatent Application No. 2011-038414 (filed on Feb. 24, 2011) which isexpressly incorporated herein, by reference, in its entirety.

The invention claimed is:
 1. A connection-structure of a flexible tube,in which said flexible tube is tightly fitted to an outer surface of anend portion of a metal pipe, comprising: an annular projection that isformed on said outer surface of said end portion of said metal pipe,said annular projection circumferentially extending over a wholecircumference of said metal pipe; a first radially enlarged portion thatis formed on a tip side of said metal pipe relative to said annularprojection, said first radially enlarged portion defining a firstannular groove with said annular projection; a seal ring that is fittedinto said first annular groove; and a second radially enlarged portionthat is formed on a base side of said metal pipe relative to saidannular projection, said second radially enlarged portion defining asecond annular groove with said annular projection; a tip portion ofsaid flexible tube being positioned on said second radially enlargedportion and close to a maximum diameter portion of said second radiallyenlarged portion.
 2. The connection-structure of a flexible tubeaccording to claim 1, wherein said first radially enlarged portion has afirst tapered surface on which a diameter of an outer surface of saidmetal pipe becomes smaller as a distance to a tip portion of said metalpipe decreases, said second radially enlarged portion has a secondtapered surface on which a diameter of said outer surface of said metalpipe becomes smaller as a distance to said second annular groovedecreases, and the tip portion of said flexible tube is positioned oversaid second tapered surface.
 3. The connection-structure of a flexibletube according to claim 2, wherein a diameter of said outer surface ofsaid metal pipe on an opposite side of said second annular groove withrespect to said second radially enlarged portion is substantially thesame as a diameter of said outer surface of said metal pipe on saidsecond annular groove.
 4. The connection-structure of a flexible tubeaccording to claim 2, wherein said second radially enlarged portion hasa third tapered surface that is inclined in an opposite direction ofsaid second tapered surface, said third tapered surface being configuredon an opposite side of said second tapered surface.
 5. Theconnection-structure of a flexible tube according to claim 2, whereinsaid second radially enlarged portion has a vertical surface that issubstantially perpendicular to the outer surface of said metal pipe,said vertical surface being configured on an opposite side of saidsecond tapered surface.
 6. The connection-structure of a flexible tubeaccording to claim 2, wherein a surface of said second radially enlargedportion, opposite to said second tapered surface, is a cylindricalsurface having substantially the same diameter as the maximum diameterportion of said second radially enlarged portion.
 7. Theconnection-structure of a flexible tube according to claim 2, wherein aninclination angle of said first tapered surface and an inclination angleof said second tapered surface are substantially the same.
 8. Theconnection-structure of a flexible tube according to claim 1, whereinsaid first radially enlarged portion has a first tapered surface onwhich a diameter of an outer surface of said metal pipe becomes smalleras a distance to a tip portion of said metal pipe decreases, said secondradially enlarged portion has a second tapered surface on which adiameter of said outer surface of said metal pipe becomes smaller as adistance to said second annular groove decreases, and the tip portion ofsaid flexible tube is positioned on said second tapered surface.
 9. Theconnection-structure of a flexible tube according to claim 1, wherein aportion of said outer surface of said metal pipe is painted up to saidsecond annular groove, to which the tip portion of said flexible tube isfitted tightly, and a portion of said outer surface from said annularprojection to the tip portion of said metal pipe is not painted.
 10. Theconnection-structure of a flexible tube according to claim 1, whereinsaid metal pipe is utilized in a fuel filler pipe for an automobile.